The present invention relates to electromagnetic apparatus and methods and Coulomb force oscillators (CFO) that generate high-density electron emission and separate and recombine electrical charge to generate electromagnetic energy such as photons and x-rays.
Recombination emission occurs when free electrons recombine with holes created by the removal of electrons resulting in the conversion of electric charge potential into electromagnetic energy. The movement, collection, and acceleration of electrons is controlled by Coulomb forces. The electric force acting on a point charge q1 as a result of the presence of a second point charge q2 is given by Coulomb's Law:
  F  =                              kq          1                ⁢                  q          2                            r        2              =                            q          1                ⁢                  q          2                            4        ⁢                  πɛ          0                ⁢                  r          2                    where ∈0=permittivity of space.
This equation satisfies Newton's third law because it implies that exactly the same magnitude of acts on q2. Coulomb's law is a vector equation and includes the fact that the force acts along the line joining the charges. Like charges repel and unlike charges attract. Coulomb's law describes a force of infinite range which obeys the inverse square law, and is of the same form as the gravity force.
  k  =                    1                  4          ⁢                      πɛ            0                              ≈              9        ×                  10          9                ⁢                  N          ·                                    m              2                        /                          C              2                                            =                  Coulomb        '            ⁢      s      ⁢                          ⁢              constant        .            
Like charges repel and unlike charges attract. Negative electrons will move toward a positive charge potential. A Van de Graff generator is a well known example of a device that can separate and store high-voltage electrical charge.
A light emitting diode (LED) exemplifies the recombination emission process. It has two sides of dissimilar material and charge separated by a junction. One side is dominated by positive electric charges and the other side is dominated by negative electric charges. The junction acts as a barrier between the p side and the n side. A few volts applied to the LED terminals will cause electrons to flow from the n side to the p side. Once on the p side the electrons are immediately attracted to the positive charges due to the mutual Coulomb forces of attraction between opposite electric charges. The two charges “recombine.” Each time an electron re-combines with a positive charge, electric potential energy is converted into electromagnetic energy. With each recombination a quantum of electromagnetic energy is emitted in the form of a photon of light. The frequency of the light is characteristic of the semi-conductor material. A material emits photons in a very narrow frequency range. Using different materials to produce LED's with the right color emission effects RGB (red, green, blue) colors. The intensity of LED emission is proportional to the charge differential between the two sides. The LED is restricted to low-voltage on the order of 0.6 to 2.6 volts DC and milliamp currents. The design is not upwardly scaleable and an emission increase can only be effected by assembling an array of multiple LED.
The conventional x-ray tube is another example of recombination emissions. High-speed electrons, emitted by a thermionic electron source and accelerated by tens to hundreds of kilovolts of potential bombard a metal target producing characteristic and Bremsstrahlung radiation. Characteristic x-rays are produced when an accelerated electron knocks an electron from the inner shell of an anode atom. Electrons knocked from the inner shell of an atom are replaced by electrons dropping down from a higher state, outer shell position. The electron gives up its higher state energy in the form of characteristic x-rays with sharply defined frequencies associated with the difference between the atomic energy levels of the target atoms.
Emitted at discrete energies, they have a discrete spectrum. Deflected electrons give up their energy in the form of Bremsstrahlung or braking radiation which occurs when negatively charged electrons in motion are deflected toward positively charged atomic nuclei or away from negatively charged atomic nuclei. Deflection is equally balanced between attraction and repulsion. Deflection strips energy from the accelerated electron.
If the deflection is away from a negatively charged nuclei the electron will loose energy in steps and may not have enough energy to dislodge a shell electron. This action broadens the Bremsstrahlung frequency and increases the number of those emissions. The greater the kinetic energy of the accelerated electron, the greater the probability that it will dislodge an inner shell electron. Increasing the voltage increases the kinetic energy and the x-ray production efficiency. An accelerating voltage of <100 kV is 0.05% efficient whereas a voltage of >1 mV is 70% efficient. As energy density increases heat becomes a limiting factor and various methods are employed in attempts to cool the system. Emission is confined to a small lens area adjacent the target anode. The emitted x-rays diverge when leaving the lens area making it necessary to move the lens a measured distance from the specimen that is to be x-rayed, meaning that full body scans require the emitter to be several feet from the body which reduces the degree of definition permitted. The closer the x-ray emitter to the specimen the greater the revealed detail.
A miniature x-ray generator, known as COOL-X, uses a pyroelectric crystal, and is marketed by Amptek Inc. of Bedford Me. The unit does not provide a constant x-ray flux, and in particular, the flux varies throughout a 2-5 minute cycle and may also vary from cycle to cycle. It is theorized that a polarization change caused by the alternate heating and cooling of the pyroelectric crystal attracts and repels electrons which alternately impact the crystal and a copper target producing characteristic x-rays and Bremsstrahlung x-rays. It appears that the emission parameters of the COOL-X miniature x-ray generator are basically uncontrollable.
As is discussed in Nanotechnology, Vol. 2, No. 4, December 2003, low-voltage electron emission from cold-cathode semiconductor devices that eject electrons into the vacuum is based on Fowler-Nordheim tunneling and has been intensively investigated for the last several years. The emission electrons are variously referred to as hot electrons, ballistic electrons, and energetic electrons. The intent is to develop high-density emitters capable of stabilized electron emission and long term reliability that may be used in flat panel displays, photolithographic equipment, plasma etchers, electron curing, solid state lighting and so on. Basic to all designs is the need to apply a voltage bias between the upper and lower layers to initiate the Fowler-Nordheim tunneling action that propels substrate electrons through the upper layer to the vacuum interface. The positive electrode is thin in comparison to the mean free path of electrons in the electrode material such that tunneling electrons travel ballistically through the positive electrode. Peak energy is virtually linear dependent on applied voltage with the maximum output restricted by current and resistance limitations.
One drawback of low voltage emitters is the lack of inexpensive low voltage phosphors. The high voltage phosphors used in high voltage applications such as CRT's lack the carriers or holes necessary to effect bright light emission at reduced voltages. Current technology produces a steady and uniform electron stream at relatively low densities and requires wigglers or other methods to increase the density by bunching electrons as is common in traveling wave tubes and linear accelerator applications.
Additional references related to x-ray emitters and displays, include “A Simple X-Ray Emitter,” H. Murakami, R. Ono, A. Hirai, Y. Hosokawa, Anal. Sci. 2005, vol. 21, “Phosphor Challenge for Field-Emission Flat-Panel Displays,” C. Hunt, A. Chakhovskoi, J. Vac. Sci. Technol. B 15(2) March/April 1997, and “New Insights in High-Energy Electron Emission and Underlying Transport Physics of Nanocrystalline Si,” S. Uno, K. Nakazato, S. Yamaguchi, A. Kojima, N. Kosida, H. Mizuta, IEEE Transactions on Nanotech., 2, 4, 2003.
It would be desirable to have apparatus and methods that recombine separated charge to convert electric potential energy into electromagnetic energy emissions.